CARINA SIGNORI DIABETES AND OBESITY JOURNAL CLUB 3/15/12

Introduction Obesity is a problem of overeating. But not all people that overeat become obese. Can diet composition affect weight gain?  An analysis of 12 human studies suggested that a diet that contains either high or low protein is less “metabolically efficient” than diet of average protein intake 1.  The greatest metabolic efficiency of weight gain (less wasting of calories) during overfeeding occurred when protein intake was 10-15% of the energy consumed.  Metabolic insufficiency (or wasting of calories) during overfeeding occurred with diets containing low or high amounts of energy from protein. 1. Stock MJ. Gluttony and thermogenesis revisited. Int J Obes Relat Metab Disord. 1999;23(11):

Overeating a diet low or high in dietary protein may maintain body weight  Because of the energy cost involved in sparing lean body mass with a low protein diet or expanding lean body mass with a high protein diet. This study was designed to determine whether the level of dietary protein affected:  Body composition  Weight gain  Energy expenditure …under tightly controlled conditions in a randomized controlled trial.

N=25 16 men, 9 females Ages years BMI % Ptn, 52% fat, 42% CHO 15% Ptn 44% fat, 42% CHO 25% Ptn 33% fat 41% CHO Randomized parallel group inpatient study where they resided for weeks with no prescribed or regular exercise.

They were fed their assigned diet the last 8 weeks of the study. Initial E content of the weight stabilizing diet was based on 24 hr E expenditure measured on day 3. E requirements for weight maintenance were established over days on an isocaloric diet (15% protein)

BMI mean 25.1 (3.0). At baseline they were similar except for race.

Changes in Weight and Fat Weight increased in normal and high protein group. Body fat composition stayed the same for all 3 groups.

Lean Body Mass and Resting Energy Expenditure Lean body mass decreased in low protein diet group Resting E expenditure increased in normal and high protein groups

Energy Expenditure increased significantly in the normal and high protein groups compared with the low protein group (p=0.07) which did not change from baseline (P=.15). The change in total E expenditure in the low protein group was less than in the normal protein group (P<0.05) There was a positive correlation between change in total energy expenditure and protein intake. (P=0.04)

Body Composition Extra E intake predicted both the increase in lean body mass and body fat. Protein intake predicted the increase in Lean body mass but no the change in fat storage. They calculated that the protein intake required to prevent loss of lean body mass was 77.8 g/d (95% CI, g/d). This is 30g/d higher than the protein level provided by the low protein diet (47.0 g/d 95% CI, g/d)

Conclusions The key finding of this study is that calories are more important than protein while consuming excess amounts of E with respect to body fat increase. The metabolic efficiency of weight gain in the low protein group was significantly higher (75.1 MJ/kg [95% CI, MJ/kg) than the high protein group (38.0 MJ/kg [95% CI, MJ/kg; P=0.04).  Normal protein was 45.5 MJ/kg (95% CI, MJ/kg). This agrees with the hypothesis that low protein diet is more metabolically efficient however there was less weight gain in this group.  90% of excess calories however were stored as fat though in the low protein group (versus 50% in the normal and high protein groups.)

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